Radio studies of mysterious Type IIn supernovae Poonam Chandra National Centre for Radio Astrophysics Tata Institute of Fundamental Research Collaborators: Roger Chevalier, Nikolai Chugai, Claes Fransson, A. Soderberg

Supernova Classification (based on optical spectra and light curve) Supernovae Hydrogen Type II Narrow H lines Type IIn No narrow H lines Type IIP/IIL No Hydrogen Type I Silicon Type Ia No Silicon Type Ib/c Plateau Type IIP Linear Type IIL Helium Type Ib No Helium Type Ic

Type IIn supernovae Very diverse stellar evolution and mass loss history. SN 1988z, extremely bright even after 20 years SN 1994w faded only in 130 days. SN 2005gl: LBV progenitor? SN 2006gy, extremely bright: PISN progenitor? SN 2002ic, SN 2005gj: Hybrid between Ia/IIN. SNe 2001em, 1995N, 2008fz: Type Ib/c properties SN 2009ip: episodic ejections before turning into true supernova

Type IIn supernovae Explosion in very dense environments Very high mass loss rates ~ M sun /Yr Very high bolometric and H  luminosities- indicative of high circumstellar interaction INDICATIVE OF HIGH RADIO LUMINOSITY

Circumstellar interaction Circumstellar wind (1E-5 Msun/Yr, v=10 km/s) Explosion center Reverse Shock ~1000 km/s Forward Shock ~10,000 km/s Ejecta Circumstel lar medium density ~1/r 

SN IIn Radio Statistics Around ~180 Type IIn supernovae So far only 81 observed in radio bands Out of 81, only 11 detected in radio bands

Poonam Chandra

Peak radio and X-ray luminosities 2009ip

Radio light curves- SN 2006jd Chandra et al. ApJ 2012, 755, 110

Poonam Chandra11 Frequency

Free-free absorption: absorption by external medium Information about mass loss rate. Synchrotron self absorption: absorption by internal medium Information about magnetic field and the size.

Radio Spectra Chandra et al. ApJ 2012, 755, 110

Radio model of SN 2006jd (Chandra et al. 2012) Internal free-free absorption. Seen in SN 1986J and SN 1988Z too. Density of emitting gas  =6x10 6 cm -3. Mass of absorbing gas required to do the observed absorption is 2x10 -8 T 4 5/2 M sun. Modest amount of cool gas mixed into radio emitting region can do the required absorption. Source of the cool gas is radiative cooling of the dense gas in the shocked region.

SN 2006jd: Main Results Radio and X-ray both give s~ (density~1/r s ). Mass loss rate ~ 5x10 -3 M sun /yr. Shocked gas density 6x10 6 cm -3.

SN 2010jl Chandra X-ray Spectra Comparison November 2010 October 2011June 2012 Chandra et al. 2012, ApJ Letters 2012, 750, L2 Mass loss rate 8E-3 M sun /yr ObservationsNovember 2010October 2011June 2012 Duration39.6 ks41.0ks39.5ks Counts Count Rate1.13E-2 cts3.29E-2 cts3.68E-2 cts Column Density9.7E23 cm E23 cm E22 cm -2 Temperature>10 keV

Causes of radio non-detections Some Type IIn supernovae are thermonuclear explosions. Extremely high absorption.

TWO SEPARATE KINDS OF TYPE IIN SUPERNOVAE!!!!

Summary Type IIN supernovae: diverse behaviour. Extremely high circumstellar interaction. Trend emerging: late radio emission. Only 5% supernovae are radio bright. Extremely high absorption supressing radio emission? Two classes of Type IIn supernovae?

Evolution of stars Poonam Chandra20

One example: SN 1995N, Type IIN Chandra et al. 2009, 2005 Observed for many years with the GMRT (Chandra, Ray etc.) Radio observations for long time with the VLA (Weiler, Stockdale, van Dyk etc.) Chandra observations in 2004 (Chandra, Ray, Schlegel, Sutaria etc.) Archival ROSAT and ASCA observations (Fox et al). Many optical spectroscopic and photometric observations (Fransson et al.)

Radio studies H  luminosity: free-free absorption dominant. Fastest ejecta decelerating with R α t Ejecta density gradient  = r -n, n=8.3. Mass loss rate: 6x x10 -4 Msun/yr for wind speeds of km/s (Use ~10 -4 Msun/yr). Reverse shock X-ray luminosity and mass-loss rate gives: n≈8, T cs ≈0.3x10 -9 K, T rev ≈0.9x10 -7 K,  cs ≈2x10 6 cm -3,  rev ≈3x10 5 cm -3.

Core Collapse Supernovae

Thermonuclear Supernovae

Suggested by Schlegel Most diverse class of supernovae. Unusual optical characteristics: – Very high bolometric and H  luminosities – H  emission, a narrow peak sitting atop of broad emission – Slow evolution and blue spectral continuum Late infrared excess Indicative of dense circumstellar medium.

Type IIn spectra

Circumstellar Interaction

SN IIn Radio Statistics Around ~180 Type IIn supernovae So far only 81 observed in radio bands 43 SN IIn observed by us in radio Out of 81, only 11 detected in radio bands 4 detected by us (SN 2005kd, 2006jd, 2008iy, 2009ip) In X-rays detected by us: SN 2006jd, 2010jl, 2009ip

VLA observations of Type IIn supernovae Poonam Chandra

SN 2006jd Chandra et al. ApJ 2012, 755, 110 Discovered October 12, 2006 in UGC 4179 Redshift z= Initial spectrum shows Type Ib and later spectrum shows IIn Radio Observations: VLA(EVLA), GMRT X-ray Observations: Swift-XRT, ChandraXO, XMM-Newton

SN 2006jd- radio observations With VLA starting from 2007, Nov UT Epoch: Day 400 until Day Frequency bands: 22.5 (K), 8.5 (X), 4.9 (C) and 1.4 (L) GHz bands With GMRT at three epochs, between 1104 day to 1290 days. Frequency bands: 1.4 GHz and 0.61 GHz bands. Not detected yet in 0.61 GHz bands.

SN 2006jd: Main Results Column density is a factor 50 smaller (1.3E21) than needed to produce the X-ray luminosity (4E22). Indicate towards global asymmetry. Lower column density also works against external FFA model. The derived external FFA optical depth from X-ray data is ~8E-4 at 5 GHz on day EW of Fe line much higher than expected. Possible region is mixing of cool gas could enhance the width of the line.

SN 2010jl Chandra et al. 2012, ApJ Letters 2012, 750, L2 Discovered on 2010 Nov 3.5 UT in UGC 5189A (z=0.011) Discovered magnitude Brightened to One of the brightest apparent magnitude. (Absolute visual magnitude M v =-20) Archival HST image show progenitor star >30Msun. Low metallicity host galaxy, Z~0.3Msun. Circumstellar expansion speed km/s.

SN 2010jl Radio Observations: EVLA : 10 observations from November 2010 until Now. No detection. X-ray observations: At 3 epochs with Chandra – Novemeber 2010 – October 2011 – June 2012 Detection at all three epochs in X-ray bands

SN 2010jl Main results Column density ~10 24 cm -2 (1000 times higher than Galactic absorption). High temperature >10 keV High temp indicates forward shock emission High absorbing column density not accompanied by high extinction of the SN. This indicates column near forward shock, due to mass loss, where dust has been evaporated. First time X-ray absorption by external medium, that is not fully ionized by the energetic medium. Fe 6.4 keV line also points to partially unionized medium.

SN 2010jl Main results Fe 6.4 keV (narrow k-alpha iron line) in the first epoch and not in the second epoch explains that ejecta has moved past the closeby partially unionized gas. The equivalent width (EW=0.2 keV) consistent with that expected for this line. Low temperature component fit by powerlaw of ~1.7 or ~1-2 keV temperature and column density is that of Galactic. Luminosity ~4x10 39 erg/s. Flux change between the two epochs is 20-30%. Consistent with a background contaminating ULX source. Also looked at the possibility that enhanced 1 kev emission is by the CNO elements. Not possible as this gives too little absorption in keV range. Origin of additional component (NH~8E22, kT~1keV) is not known.

SN 2010jl Main results Luminosity ( keV) ~7x10 41 erg/s, amongst most luminous X-ray supernovae. Since most emission > 10 keV, this is spectral luminosity Ejecta speed (v=sqrt(16 kT/3  ) > 2700 km/s. Mass loss rate > 4x10 -3 Msun/year

Circumstellar Interaction: Absorption Processes

Trace back the history of the progenitor star since wind velocity ~10 km/s and ejecta speeds ~10,000 km/s. Supernova observed one year after explosion gives information about the progenitor star 1000 years before explosion!!! Circumstellar interaction